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| Powering cheap 10w LED from eBay |
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| skillz21:
--- Quote from: sleemanj on August 07, 2019, 12:56:21 am ---Ok there is either, a> something wrong with your measurement/supply; or b> these are not bare leds post a photo of the led, or a link to the listing. You drive bare LEDs with a constant current (or at least with a suitable resistor to limit the current), typical 3x3 die arrangement 10W leds should be run at about 900mA, and the much less typical single series arrangement of die should be run at about 300mA. --- End quote --- Here's the link: https://ebay.us/zCxCaz. I bought the cool white. |
| sleemanj:
Listing doesn't say but I'd wager they are 3x3, and there is something wrong with your measurement setup or supply. You should have no trouble, with a current limited supply which is capable of providing 10W at 10-12v, of pushing 900mA through these. At it's most basic, get a 12v 1A+ supply, and a 2.7 Ohm 5 Watt Resistor will be in the ball park. Remember you can measure voltage drop across the resistor and calculate current rather than adding multimeter current shunt into the mix. |
| skillz21:
--- Quote from: sleemanj on August 08, 2019, 10:16:40 pm ---Listing doesn't say but I'd wager they are 3x3, and there is something wrong with your measurement setup or supply. You should have no trouble, with a current limited supply which is capable of providing 10W at 10-12v, of pushing 900mA through these. At it's most basic, get a 12v 1A+ supply, and a 2.7 Ohm 5 Watt Resistor will be in the ball park. Remember you can measure voltage drop across the resistor and calculate current rather than adding multimeter current shunt into the mix. --- End quote --- I have a buck converter that is capable of supplying up to 3A (I tested by setting a current limt and shorting the output), If this is the case, I also tested with a much beefier power supply, still the same result. What's the difference between using a resistor and the built in current shunt of my multimeter?? |
| sleemanj:
Once again, LEDs are current controlled. Your current shunt in your multimeter is like 100mR maybe. The forward voltage of a white led is around 3-3.3v, your LED will have a 3x3 arrangement giving a forward voltage of 9-10v. You supply 12v, through a 100mR resistor (shunt) to your 9-10v LED, how much current are you pushing (or attempting to make the power supply push), use Ohm's law. |
| skillz21:
--- Quote from: sleemanj on August 09, 2019, 06:41:19 am ---Once again, LEDs are current controlled. Your current shunt in your multimeter is like 100mR maybe. The forward voltage of a white led is around 3-3.3v, your LED will have a 3x3 arrangement giving a forward voltage of 9-10v. You supply 12v, through a 100mR resistor (shunt) to your 9-10v LED, how much current are you pushing (or attempting to make the power supply push), use Ohm's law. --- End quote --- I feel like I'm missing something here, so please correct me if I'm wrong. The listing said 9-12v, so I'm guessing that it's fine to drive them at a bit higher than their forward voltage... right? As for the current, going off their maximum recommended voltage of 12v, I should be trying to push about 830mA to achieve the advertised 10w... right? |
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